The present invention relates to tools for minimally invasive techniques, particularly to tools including catheter tips, actuators, etc. which use shape memory materials, and more particularly to minimal by invasive devices that have reversible translation and/or bending articulation capability to enable find positioning of tools, therapeutic device positioning, or therapeutic catheters by a guide catheter.
Biological and surgical micro electromechanical systems (MEMS), useful for their ability to be placed into and easily maneuvered around within the body, are being touted as the fastest growing area of micro-systems. For example, microcatheters are used in many medical applications for minimally invasive surgery. There are presently over 700,000 surgical uses of catheters per year in the United States, representing a market of many hundreds of million dollars.
As surgeons in the medical field continue to adopt and perform advanced surgical procedures, the miniaturization of medical devices is taking place and allowing surgery with small external incisions that grants access for these microsurgical tools by way of catheters. With roots in laparoscopic surgery (entering the abdomen through the navel and small holes in the midsection), minimally invasive surgery can currently be performed by inserting catheters in the femoral artery at the base of the thigh, navigating the blood vessels around the body, and arriving at problem areas like the heart or brain. Once the distal tip of the catheter is precisely placed inside the body, a microsurgical procedure like balloon angioplasty, stent placement, localized cauterization or drug delivery can take place. With the reduced bodily reaction to microsurgery and the minimization of scar tissue, these procedures are highly preferred over more typical “macro” surgery.
Surgeons who work with catheters have expressed a need for easier, more precise placement of the distal tip of the catheters. Upon rough placement of the tip (within ˜2 cm), it would be advantageous to hold the proximal end of the catheter (toward the outside of the patient) 90% of the catheter in place, while articulating the distal end 10% with high accuracy and precision.
While catheter tubes have been created to fit through the vessels in the brain, these vessels are very tortuous and difficult to navigate with current techniques. The need exists for a method and means for articulating the distal tip to aid in maneuvering through the labyrinth of smaller diameter vessels like those in the neurovascular system.
Stents have been used in minimally invasive surgical techniques to open clogged arteries and veins to restore somewhat normal blood flow or to strengthen weakened vessels by adding a high modulus “patch” to the vessel wall. Stent problems needing a solution are reliable deployment (placing the stent correctly) and restenosis due to scalloping (an effect arising from the lack of a solid wall around the stent where materials can push through the stent's net-like weave and continue to occlude the vessel after the attempt at repair).
As pointed out above, the vasculature-especially the neurovasculature-is extremely tortuous forcing the catheter to follow several bends and turns before reaching its target destination. At times, abrupt turns into branching arteries are required. As a result, frictional effects between the catheter and vessel wall lead to a deterioration of the catheter tip maneuverability and control as more and more of the catheter is fed into the body. Static friction causes the catheter tip to bind, even when guide wires are used, which in turn causes the catheter to bunch up. Thus, there is a need for solutions to this problem, which are provided by the present invention and include a variable modulus catheter, a catheter with vibrational mode, an inch worm catheter, and a catheter with an articulating tip.
During the past decade, numerous approaches to solving the above-mentioned catheter related problems have been proposed, with many of the approaches involving the use of shape memory materials. Numerous papers, articles, and patents have been directed to these shape memory materials, as exemplified by H. Tobushi et al, “Thermomechanical Constitutive Modeling in Shape Memory Polymer of Polyurethane Series,” Journal of Intelligent Material Systems and Structures, Vol. 8, pp. 711-718, August 1997; H. Tobushi et al, “Mechanical Properties of Shape Memory Polymer of Polyurethane Series (Basic Characteristics of Stress-Strain-Temperature Relationship),” JSME International Journal, series 1, Vol. 35, no. 3, pp. 296-302, 1992; G. Bourbon et al, “Three-dimensional active microcatheter combining shape memory alloy actuators and direct-drive tubular electrostatic micromotors,” SPIE-Int. Soc. Opt. Eng., pp. 147-158, 1998; P. Krulevitch et al, “Thin Film Shape Memory Alloy Microactuators,” Journal of Microeletromechanical Systems, Vol. 5, no. 4, pp. 270-282, December 1996; E. P. George et al, “Materials for Smart Systems Symposium,” Maler, U.S. Patent Res. Soc. 1995, pp. 369-74; U.S. Pat. No. 5,405,337 issued Apr. 11, 1995, to R. S. Maynard; and U.S. Pat. No. 5,944,710 issued Aug. 31, 1999, to W. R. Dubual. Also see Japanese Patent Abstracts: JP 9109320A involving shape memory apparatus, for blow deflection flap driving mechanism etc, comprising shape memory composite member, Pettier device and heath radiator, providing high corrosion resistance and insulation properties; J1 81999080A involving shape memory composites, e.g. for endoscopes, temperature display, etc., comprising shape recovery temperature of shape memory alloy martenesile, and temperatures or generating power of alloy and polymer are identical; JP 7209571A involving high polymer molding product having reversible shape with temperature change prepared by making high polymer molding and shape memory alloy into composite product, etc.; JP 3059142A involving shape memory composite material-comprises woven filaments of shape-memory alloy, resin, etc., optionally in cylindrical form, optional of different shapes and shape-recovering temperatures; and JP 302-3379A involving shape-memory composite material used as spring, etc.-obtained by connecting shape memory parts of nickel-titanium alloy or polynorbomane-polystyrene-polybutadiene copolymer, with a connector.
The present invention provides solutions to the above-mentioned catheter related problems by the use of shape memory alloy (SMA), shape memory polymer (SMP) and combinations of these two shape memory materials which have bistable characteristics. The innovation of the present invention involves tools with reversibility capabilities fine positioning of the tools or distal end of the catheter, as well as reversible bending articulation of the distal tip, along with catheters having a variable modulus or vibrational mode and inch-worm capabilities as well as an articulated tip.